


Sherlock Holmes and the Plight of the Black Rose

by catharsis_in_a_bottle



Category: Harry Potter - J. K. Rowling, Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: (you'll see what i mean), Alternate Universe - Harry Potter Setting, Aurors, BAMF Mrs. Hudson, Black Rose, Developing Sherlock Holmes/John Watson, Eurus Holmes Is... Interesting, Gryffindor John Watson, Hogwarts Express, Hogwarts Houses, Jealous John Watson, Jim Moriarty is a Little Shit, Lestrade Is Not A Good Detective, Ministry of Magic, Multi, Platform 9 3/4, Ravenclaw Sherlock, References to Drugs, Sherlock Characters as Hogwarts Professors, Sherlock Harry Potter AU, Slow Burn, of course, will add more tags, yay
Language: English
Status: In-Progress
Published: 2020-09-06
Updated: 2020-09-23
Packaged: 2021-03-06 21:15:28
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,028
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26325499
Author URL: https://archiveofourown.org/users/catharsis_in_a_bottle/pseuds/catharsis_in_a_bottle
Summary: The rumors spread like dragonfire. There’s a new Dark wizard rising to power in the shadows, they say; the nameMoriartyis whispered on trembling lips. The Ministry, they say, has been infiltrated by a mysterious witch of equally mysterious intentions. And everyone is curious about the new arrivals at Hogwarts, among them Professor Watson, the new Care of Magical Creatures teacher, and the newly appointed Headmistress:Eurus Holmes.The wizarding world is entirely unprepared for the malevolently organized chaos about to hit them over their heads. And that’s where Sherlock Holmes comes in. He’s a self-proclaimed investigative consulting Auror, a Defense against the Dark Arts professor, and most importantly, the cleverest man ever to grace the halls of Hogwarts (or so he says) - and perhaps the only one who can prevent the crumbling collapse of the entire wizarding world.Edit: it's highly improbable that I will continue writing this
Relationships: Irene Adler/A Lot Of Random People, Mary Morstan/Molly Hooper (maybe?), Mary Morstan/Smiling A Lot, Mycroft Holmes & Sherlock Holmes, Sebastian Moran/Jim Moriarty (background), Sherlock Holmes & John Watson, Sherlock Holmes/Drugs, Sherlock Holmes/John Watson
Comments: 3
Kudos: 13





	1. New Arrival

**Author's Note:**

> Welcome, folks, to the beginning of an experiment. Hypothesis: If I insert Sherlock characters into the Harry Potter universe, then I will create a very weird and hopefully intriguing story, because crossovers tend to be rather interesting. 
> 
> Although I did receive online inspiration, I sorted the characters into different Houses as I pleased. The plot is mine; several aspects of the story, however, are based upon aspects of Harry Potter. Who needs slithering, noseless Voldemort when you can have a seductive, psychopathic Jim Moriarty as a Dark wizard?
> 
> I would like to thank my wonderful friend for her enthusiasm, input, and general awesomeness. I would also like to thank the BBC for gracing this planet with our lovely high functioning sociopath, whom I will now proceed to turn into a wizard.
> 
> This work does not have a beta, and it has not been Britpicked. My very American apologies for any mistakes. Would you like a biscuit?
> 
> And now, without further ado, I present to you the epic tale of Sherlock Holmes and the Plight of the Black Rose. Enjoy.

**Summary for the Chapter:**

> Professor Watson, about to start his first year at Hogwarts, meets a curious man on the Hogwarts Express before discovering that he has an even more curious sister.

Platform nine and three-quarters is a bustling collision of nostalgia, mayhem, and debilitating stress. There’s the bright red steam engine - _fantastic to see you again, the memories, wow_ \- the robed blurs dashing about - _come back, Delia, you’ve forgotten your owl_ \- and the fact that _oh no_ , this will be John Watson’s first time at Hogwarts and he starts teaching _tomorrow_. The emotions blend and become a good, solid headache. 

He tries to call himself Professor Watson in his head. It feels too _formal_. He’s been training for this for years, and yet it’s still difficult to call himself anything other than _John_. John Watson, the Healer, the Gryffindor, and now the teacher.

John steps up into a train carriage and hauls three suitcases up after him. Then, slightly out of breath, he makes his way past nervous students, offering them comforting smiles, before shutting himself in an empty compartment towards the back of the car. His robes get caught in the door, and he grunts and rips them free. He manages to shove his suitcases into the luggage compartment before collapsing onto a cushioned seat, letting out a long breath as he turns to stare out the window. Parents hustle little first years up into carriages and hug older children goodbye. Owls flap around in cages. Teary-eyed families wave at the windows as the train begins to pull away. John smiles. 

He’s about to slip into a light doze when the compartment door snaps all the way open with a _crack_. John startles, looking up to face a rather haphazard looking man with dark hair that tumbles down to his ears in loose curls, pale-moon skin that ends in angles anywhere you follow it, and black robes that appear to have been thrown on hastily by a horde of garden gnomes. He’s quite tall. 

“Anyone sitting here?” says the man in a deep baritone, staring John down with steely eyes the color of sea foam. 

John has to take a second to collect himself before shaking his head and gesturing vaguely towards the seat opposite him. The man tosses a duffel bag up into the luggage compartment, flops into the seat, and promptly procures a newspaper from somewhere inside his mass of robes. He begins vigorously scanning the page. He’s holding it upside down. 

John clears his throat. “Erm,” he says. The man does not look up. “Erm…” he says again. “My name is John. John Watson. Professor Watson.”

“Care of Magical Creatures instructor, yes?” replied the man, running his pointer finger swiftly along a line of ink before rather aggressively flipping the page, the crinkling paper momentarily adding to the cacophony started by the deep hum of the train.

“... Yes,” John says, blinking a few times. Then, when the man doesn’t say anything, he adds, “And… you are?”

The man looks up and gives a very faint smile that fails to reach his eyes. “Sherlock Holmes. Ravenclaw. Defense against the Dark Arts. Investigative consulting Auror.”

“Consulting Auror?”

“ _Investigative_ consulting Auror.”

“Huh. That paper’s upside down, you know.”

Sherlock rolls his eyes. “No, I didn’t notice.”

Despite himself, John grins a little. “You don’t seem like the type who likes children,” he says.

“Some of them are tolerable,” mumbles Sherlock, finally turning the newspaper upright and intensely furrowing his brow before shoving the whole thing back into his robes with a sigh. He puts a finger on his chin, thinking. “I suppose the appeal of teaching, for me, is really just making them less idiotic. Passing on skills. Helping them to be… _more_ tolerable.”

John chuckles and leans back in his seat. “How long have you been teaching?”

“Three years.” Sherlock sounds bored. 

“Alright,” says John. “And how do-”

“How do I like it?” Sherlock cuts in, clearly annoyed. John is taken aback by his severeness. “It’s my _life_. Now must we _really_ keep up the small talk? It’s all rather useless.”

John narrows his eyes. “I just thought,” he says, trying and failing to sound as if he is surrendering, “that we might get to know each other a bit, since we’ll be working together-”

“Get to know each other?” Sherlock leans forward in his seat and gives John a very peculiar once-over; his gaze ghosts over John’s face, his robes, his shoes, and even it would seem his soul, from the sudden arrowhead sharpness of those eyes. Then he leans back and makes direct eye contact. John’s nerves jump, an electric sensation.

“I know you fought in the war,” Sherlock begins. His words are fast and matter-of-fact. “You fought against the Dark wizard Magnus before he was defeated. You were a Healer then, and afterwards you moved to St. Mungo’s in search of a more peaceful approach to your oath. You’re a Gryffindor. You have a Slytherin sister from whom you are estranged. You pretend to enjoy the company of the general populace, but you prefer to be alone or only with the particularly interesting, which is why you took up the Care of Magical Creatures position. And you were raised by relatives, but your parents left you a fair amount of money before misfortune befell them.” He crosses his legs and narrows his eyes. “Quite enough to be going on, I think.”

John doesn’t move. The air is completely still. Sherlock seems to be entirely unaffected by the silence.

Finally, it’s broken by a hypothesis from John: “So you’re a Legilimens.”

“No,” Sherlock says.

“You’re absolutely sure you’re not a Legilimens?”

“Quite sure. I simply _observe_ where others merely _see_. For example, I knew about your parents because your robes and supplies are newly purchased and relatively expensive, but Healers are paid horrendously, and teachers aren’t much better. Therefore you received a considerable inheritance, therefore your parents weren’t in the picture, etcetera, etcetera.”

John is doing a fantastic job at keeping his breathing even. He looks down at the carpeted floor as the train hums and hums and hums, imagining for a moment the air outside whizzing around his face and pushing back his hair. Then he says, quietly, “My father was an alcoholic. My mother left him. I never saw her again. I lived with my aunt. Harry and I - Harry’s my sister - we didn’t know we had magic ‘til she got her letter and got sent off to Hogwarts.”

Sherlock studies John’s face as if searching for something. “Nice little backstory,” he mutters.

John smiles and his eyes frown. “Yeah,” he sighs. “Nice. Don’t really know why I said that.”

He hesitates and seems to struggle with himself for a moment, and then he sticks out his hand.

“Here,” says John. ”You’re interesting. Help me survive my first year?”

Sherlock raises his eyebrows for a second, but then he slowly reaches out his hand, take’s John’s, and shakes it.

“Yes,” he agrees, the both of them feeling as if a contract has been signed, the sudden permanence completely and utterly unexpected.  
  


* * *

  
  
Teachers don’t usually ride the Hogwarts express, and so John and Sherlock receive a lot of curious stares as they haul their bags down the corridor and off the carriage. John smiles at all the peering eyes; Sherlock ignores them. _It’s going to be an interesting year_ , they both say to themselves. 

It doesn’t matter how many times one sees Hogwarts School of Witchcraft and Wizardry - it’s always the most spectacular sight in the world. The sun shines down upon the towering turrets from a cloudless sky. The sheer _size_ of the castle is almost incomprehensible. In the distance, a flock of rather large and suspicious looking birds fly lazily over the glimmering lake, where a tentacle can be seen waving through the air in the shallows before crashing back into the cool water with a splash. The forest waves lazily beyond the castle, looking almost welcoming, if it weren’t for the darkness within that even the glaring sun fails to penetrate. 

The two professors step quickly along the stone passageway up to the oak front doors. John pulls out his wand and places a locomotion charm upon his trunk so that it bobs along behind him; Sherlock simply hoists his duffel bag up over his shoulder, his perpetually glum expression not affected in the slightest by the sunlight or John’s smile. 

The oak doors are thrown open right before they reach them, and they find themselves face to face with a witch, perhaps somewhere in her late thirties, whose grin shines as brightly as the sun. Her hair is blond, wavy, and pulled back; her brown eyes crinkle at the edges as she smiles; and she wears robes of a deep, shimmering blue, topped off with a pointed sky-colored hat to match.

“Watch out for her,” Sherlock mutters into John’s ear, scowling. “Her serotonin wouldn’t cease to flow even if she awoke to Magnus having tea in her sitting room.”

“Nothing better than a new arrival!” says the witch, holding out her arms as if facing a stadium. “I’m Professor Morstan - but you can call me Mary in the off hours.” If at all possible, she grins even wider and gives the two professors a wink; John’s smile widens and Sherlock looks even more disgruntled. 

“I’m the Deputy Headmistress,” says Professor Morstan, stepping aside to let John and Sherlock pass through the doors. The doors shut behind them with a thud that shakes the magnificent entrance hall. Then she turns to face John, extending her hand. He shakes it. “And I also teach Transfiguration. Lovely bunch, those kids are. Welcome, Professor Watson.”

Professor Morstan turns to Sherlock, whose scowl lessens considerably as he peers at a suit of armor standing by the entrance to the Great Hall. She grins at him with just a touch of mischief. “And welcome back, Professor Holmes,” she says, narrowing her eyes. “No taking over the library this year, alright? We need at least _one_ professor with a proper sleep schedule.”

Sherlock turns to her and smirks. “No promises.”

Professor Morstan rolls her eyes. “You can scuttle off to your quarters now, Professor Holmes. I expect you don’t need to meet the new Headmistress.”

“No,” replies Sherlock in his deep, smooth voice. “I expect I don’t.”

He turns and takes long strides down a cavernous hallway, his black robes billowing behind him.

“You’ll get used to him,” whispers Professor Morstan, smiling again at John. “Now-”

“Holmes,” John cuts in, scratching his temple. “The Headmistress shares his last name - is he-”

“Her older brother,” she answers. “Yes. And the funny thing is, he doesn’t seem to mind at all.”

John cranes his neck and peers down the hallway, where Sherlock rounds a corner with a dramatic swoop of his robes and disappears from sight.

“He _is_ a bit funny,” John mumbles.  
  


* * *

  
  
They meet the Headmistress in a hallway lined with windows that giants could easily step through. She is as ethereal as John could have imagined. She’s a young witch in off-white robes with silver threads sewn through them, so that they shimmer even with the smallest of movements. Golden stars and moons are embroidered onto the cloth, and the whole assembly is cinched at the waist with a pearlescent white belt. Her hair falls down over her shoulders, dark and wavy. But the most intriguing feature is her eyes - the way they seem to shift colors in the light, the way they almost never blink, the way they pierce right through you in a way even more powerful than Sherlock’s. 

Everyone has heard of her. She is inarguably the most incandescent witch of the era; even her look gives that away, how she wears an expression that says _I know who you are_ , how your hopes of outsmarting her evaporate as soon as she lays eyes upon you and deduces the heart out of you. One time, she says to John, “I know your type. I know you. Gryffindor, not quick to become attached, but god how you hate being alone right now, Professor Watson. How strange for you. My brother seems to have presented an opportunity for _connection_.” 

Everyone knows that she brought down the Dark wizard Magnus, that when he tried to seize every Ministry in Europe she fought him off in less than five minutes and had him shipped off to Azkaban. She graduated from Hogwarts a year and a half early and then went to live mysteriously in the shadows, finally emerging many years later when Magnus’s powers became too great - but not nearly great enough for hers. John’s every expectation is met - he is intrigued, he is terrified, and he kind of wants her autograph. 

“Hello, Ma’am,” he breathes. 

“Hello, Professor Watson,” she says, smiling strangely and tilting her head. 

“I am Madame Eurus. Welcome to Hogwarts.”


	2. Whispers

**Summary for the Chapter:**

> The Daily Prophet spreads rumors; Sherlock collects them; Mycroft manages them; and John - his part in the scheme is just beginning.

Within just the first few days of sharing a common room with Sherlock Holmes, John learns that the peculiar man has three unceasing habits: refusing to eat until John is forced to grab him food from the kitchens, locking himself in his quarters for hours on end when he isn’t teaching, and littering the common room with newspapers and notes and parchment of all kinds. At first, all of it is quite annoying; after a while, it’s only the ocean of papers that irks John. Sherlock refuses to tell him what he’s doing with every issue of the Daily Prophet for five years in a row heaped on the sofa, and at this point John is too afraid to ask. 

On the weekends, Sherlock disappears. Leaves the castle. “Investigative business,” he tells John whenever Professor Watson dares to ask. Professor Holmes provides many mysteries, and John is determined to solve them.

But teaching always takes his mind off his enigma of a roommate (sort-of roommate - their rooms, tucked away into the castle’s thick stone walls, are right next to each other, and they share a small sitting room. Sherlock insisted on calling it a common room, and of course his opinion reigns supreme.) John spends most of his time outside the castle, down by the edge of the forest. He’s good at working with people, yes - but animals are his forte. They don’t snipe at him every time he leaves a cup of tea sitting in an inconvenient spot, and they certainly don’t give him piercing once-overs and relay to him every action he took in the last twenty four hours. They are, in short, an escape from his overbearing roommate, as well as the unpleasantries of peer-based social interaction. 

He particularly enjoys the first years. They’re wide eyed and deeply interested in everything he has to say, even down to flobberworm care. In his first week, he brings in Augureys; they’re thin, gaunt black-and-green birds that let out moaning cries before it storms. The first years pick Chizpurfle parasites off the Augureys along Professor Watson’s encouragement. 

On an overcast Friday, the winds sweep over the grounds and force the first years into warmth huddles as John makes his way back up to the castle. Once inside, he waves to a babbling cluster of older Gryffindors, who all grin back at him. He’s rather partial to members of his own house, of course - how could he not be?

“Stay out of trouble,” he remarks, still smiling. Then he slips through a hidden entrance behind a fraying tapestry and makes his way to the common room, the only minor setback being a vanishing stair that seems to have escaped his memory. 

Sherlock, as always, is sitting on the sofa surrounded by issues of the Daily Prophet.

“Right,” says John, frowning. He’s resigned. “You going to tell me what you’re up to with all those?”

Sherlock does not respond.

“ _Professor Holmes_.”

Sherlock looks up, startled, and lets out a hum of acknowledgment. “Yes, that’s me.”

“Get the Daily Prophet off our sofa.”

“Erm… no, can’t do that. Searching for a Dark wizard.”

The Prophets are quite literally mountainous. Sherlock is practically buried.

“Sherlock,” says John, sighing. “Why?”

“Surely you’ve heard of Moriarty,” Sherlock responds, making to bury his nose back in a paper. But John steps forward and physically rips it from his hands. The paper falls to the floor with a light thud. Sherlock looks up into John’s admonishing face. 

“You are a teacher,” says Professor Watson. “ _He_ … is a job for the Ministry.”

“I beg your pardon, but the Head of Magical Law Enforcement happens to be a man of almost total incompetence. So if you could allow me to be of some assistance in avoiding our potentially impending doom -”

“ _Total incompetence_? And _you’re_ better?”

Sherlock’s eyes narrow. “Yes,” he says. “Yes I am. Would you like to come with me this weekend when I leave? Would you like me to _show_ you?”

John doesn’t say anything. Not even as Sherlock begins to dig through the newspapers, scattering them on the ragged little carpet, fervently searching for buried treasure. He emerges with a headline - 

_Pewett Family Found Dead on Ireland Vacation._

“You cannot possibly understand,” Sherlock begins, his voice low as his eyes cut right through the other man. “Have you seen the growing number of deaths? The kidnappings? Remember the sabotage on the Ministry shipment to America? This is not mere _coincidence_. Remember the man who left the Ministry. _James Moriarty_. He disappeared into the shadows after orchestrating the assassination of one Hemmings Flowerby, the head of the Misuse of Muggle Artifacts department.”

Sherlock grabs another paper. _Rumors Abound around the Black Rose_ , it’s titled. John swallows audibly.

“ _This_ ,” says Sherlock through gritted teeth, “is what is upon us. You have seen nothing, you have heard _nothing_ , the Ministry has _done_ nothing because they are too afraid, and of course at Hogwarts we are safest - but _he needs to be found_.”

John remembers the Black Rose. He remembers the days when the Daily Prophet spoke of an unreachable organization behind all the chaos that came in the wake of the Dark wizard Magnus - those side crimes weren’t a big enough problem for Eurus Holmes, but they were substantial. No one, however, has ever tied James Moriarty to the Black Rose, and it is this that scares John most. Because yes - Moriarty, the cold-blooded killer who has not been seen in a decade, the man who stole the headlines for a month, is not a certified madman, but rather a certified genius merely _bordering_ on mad. But why would the Black Rose be acting up now, and why would James Moriarty be behind it?

Sherlock’s gaze never wavers. “John,” he says. “Come with me to the Ministry tomorrow. See what happens outside of Hogwarts. Come see the way the world works for me.”

And what else can Professor Watson do, standing there in the waning light, an old fear long left in the dust now resurfacing, besides nod and accept?  
  


* * *

  
  
_Report: Juliana Cummings. 5’ 6”. 158 lbs. Blonde.  
Status: Missing, hostage to unknown party.  
Last commissioned to London on a small case of attempted robbery on a bewitched house. Was wearing navy robes. Had made no contacts beforehand; family has not seen her. Unknown party demands five thousand galleons. Found in ransom note was -_

Mycroft Holmes drops his quill with a huff. He has been wearing the same black three-piece suit for four days; undoubtedly, it may stretch into a fifth. The case of Julia Cummings would be filed on standard Auror procedure, were it not for the sign of the Thorn in the ransom note. It’s a black vine entangled around a shrivelled hand, floating eerily just above the surface of the paper, swirling and taunting. Two possibilities arise: either this is someone’s horrible idea of a joke, or the Black Rose has begun to resurface. 

Having Eurus Holmes as a sister makes Mycroft work to surpass her - though he knows (and so does everyone else) that it is futile. Having Sherlock as a brother mainly causes him great stress, which it is his goal to ignore. Mycroft thinks of the three as a Trinity - Sherlock: the chaos, himself: the brains, and Eurus… the angel from hell with wrath and intellect to smite them all. But right now, it’s the chaos that he needs. He delicately shifts Juliana’s _Missing_ file aside. “ _Accio Parchment_ ,” he says, his wand still in his coat pocket, and out of a dark cabinet in the corner of the office comes a slip of paper. He dips his quill in ink.

_Brother mine,  
Although I am aware that you have unofficially commissioned yourself to my current undertaking, I hereby send my entirely official word. Whispers spread around the Black Rose, but evidence positively abounds. I need you in London tomorrow. We have an ‘anonymous party’ holding one of our officials hostage; we suspect our old friend Jim. Be prompt.  
-MH_

Signed. Sealed. Then he takes out his wand, gives it a lazy flick, and sends the letter zooming out into the hallway, where an owl will surely find it. 

The rumors are spreading in the headlines. But here, even with only a minor position in the Ministry… murder is clear as day and foul play grows darker by the day. Mycroft’s forehead is turning into a bit of an accordion, and his hair has begun to show the first signs of grey. The burden must not be alleviated, but rather shared with someone whose competence is well needed - the world’s first and only investigative consulting Auror.  
  


* * *

  
  
The tawny owl bursts into the little common room at ten when the sky is black; it nips Sherlock on the ear rather halfheartedly, drops a very small letter into his outstretched palm, and makes its way back out the window. From his armchair, John watches Sherlock tear at the seal and scan the lines almost frantically. His pale face is outlined in the candlelight. It makes him look almost like a ghost. 

“ _Tomorrow_ ,” he mutters distractedly, looking up at John. “See, I’ve been commissioned anyway. We’re going to the Ministry tomorrow.”

John purses his lips for a moment before asking, “Who commissioned you?”

A sour look seeps into Sherlock’s shadows. “My dear brother,” he says with a scowl.

“You have another sibling?”

Sherlock smiles bitterly. “Oh yes,” he says with the air of someone running short on time. “Everyone hears about Eurus, of course. No one hears about me, the _weird_ one - and of course no one hears about Mycroft, as he’s consigned himself to filing paperwork for our crumbling Ministry.”

“... the Ministry isn’t crumbling.”

“Oh, no, no, not yet, but it _will_ if my predictions…” He trails off and begins poking around the room very quickly, evidently looking for something.

“ _Accio Quill_ ,” John mutters with a sigh. An eagle feather rushes into his hand; he sends it over to Sherlock with a flick of his wand.

“Ah!” Sherlock exclaims. He procures a piece of parchment from somewhere deep inside his robes, and then he mutters as he writes. “Brother dear… Be there at eight… bringing someone… found leads in the Prophet… nothing certain. _There_. Damn, I shouldn’t have sent that owl off.”

Sherlock turns to John, his mind finally settling down enough to look him in the eye. 

“Professor Watson,” he says, inhaling deeply. John simply looks up at him from the armchair.

“Professor Watson,” Sherlock repeats. His brow furrows, and his speech is suddenly much softer. “If I am at any point rather… overly consumed by my work… I hope that your presence may bring me back to reality. I need you at the Ministry tomorrow. I hope you know that you won’t merely be for show. I… will now go off to the Owlery.”

And with one single backward glance, he hurries from the room in the dark swirl of robes that John has come to expect. 

It’s all a bit too much to take in. But Professor Watson isn’t a Gryffindor for nothing. It’s face first tomorrow, he supposes, and into the thick of it - after all, he often admits to himself that he _enjoyed_ the war against Magnus, that being a Healer and being occupied was all that kept him alive. So it is, then; maybe he’s drawn to death, and maybe he’s jumping into it again.

**Notes for the Chapter:**

> I apologize for this rather late update; I really don't have much time to write at all. I am fueled only by willpower, coffee, and overindulgence on the internet.


End file.
